Results

A total of 81 subjects (39 AS patients and 42 controls) were included for analysis.
The average age of AS patients was 47 years and the average disease duration was 22
years. AS patients were predominantly male; 76% were HLA-B27-positive. Median fCAL
levels were 42 μg/g and 17 μg/g in the AS group and controls, respectively (P < 0.001). When using the manufacturer's recommended cutoff value for positivity of
50 μg/g, stool samples of 41% of AS patients and 10% of controls were positive for
fCAL (P = 0.0016). With the exception of ANCA, there were no significant differences in antibody
levels between patients and controls. Median ANCA was 6.9 ELISA units in AS patients
and 4.3 ELISA units in the controls. Among AS patients stratified by fCAL level, there
were statistically significant differences between patients and controls for multiple
IBD-associated antibodies.

Conclusion

Calprotectin levels were elevated in 41% of patients with AS with a cutoff value for
positivity of 50 μg/g. fCAL-positive AS patients displayed higher medians of most
IBD-specific antibodies when compared with healthy controls or fCAL-negative AS patients.
Further studies are needed to determine whether fCAL can be used to identify and characterize
a subgroup of AS patients whose disease might be driven by subclinical bowel inflammation.